road construction activity

Topics: Construction aggregate, Bitumen, Asphalt concrete Pages: 35 (2337 words) Published: February 25, 2014
Construction & Quality
Control of Flexible
Pavements

BITUMINOUS PAVEMENT
CONSTRUCTION
Bituminous construction are classified
into four categories
• Interface Treatments
• Thin Bituminous surface Courses
• Bituminous Surface Courses
• Bituminous Binder Courses

INTERFACE TREATMENTS
Prime Coat
Tack Coat
Crack Prevention Courses
SAM and SAMI

Purpose Of Priming:
To plug the capillary voids
To coat and bond loose materials on the surface
To harden or toughen the surface
To promote adhesion between granular and the
bituminous layer

Choice of Primer


The primer shall be bitumen emulsion, complying
with IS 8887 of a type and grade as specified (SS-1)



The use of medium curing cutback as per IS 217
shall be restricted only for sites at sub-zero
temperatures or for emergency applications

REQUIREMENT FOR PRIMING
MATERIAL
Porosity

Type of
Surface

Viscosity at Quantity
600 C
per 10 m2
(Kg)
(centistokes)
30-60
6-9

Low

WMM,
WBM

Medium

Gravel
base

70-140

9-12

Cement
Stabilised
soil base

250-500

12-15

High

TACK COAT
Purpose of Tack Coat:
To ensure a bond between the new construction and
the old surface

Material for Tack Coat:
The primer shall be bitumen emulsion, complying
with IS 8887 of a type and grade as specified (RS-1)

Use of Cutback:
It should be restricted for sites at subzero
temperatures or for emergency applications

RECOMMENDED QUANTITIES OF
MATERIAL FOR TACK COAT
Type of Surface
Bituminous Surface

Quantity in kg
per m2 area
0.20 to 0.25

Dry and hungry bituminous
surfaces
Primed granular surface

0.25 to 0.30

Unprimed granular base

0.35 to 0.40

Cement concrete pavement

0.30 to 0.35

0.25 to 0.30

WRONG PRACTICE OF TACK COAT

INSUFFICIENT TACK COAT

MECHANICAL PRESSURE
SPRAYER FOR PRIME/TACK COAT

MECHANICAL PRESURE HAND
SPRAYER FOR PRIME/TACK COAT

Properly Done Tack Coat

20-30% more quantity of tack coat for milled surface

Thin Bituminous Surface
Courses

OPEN GRADED PREMIX SURFACE
Quantities of materials required for 10 m2 (20 mm)
Aggregates
a. Nominal stone 13.2 mm (22.4-11.2)
b. Nominal stone 11.2 mm (13.2-5.6)
Total
Binder
a. For 0.18 m3 of 13.2 mm nominal
size at 52 kg bitumen per m3
3
b For 0.09 m of 11.2 mm nominal size
at 56 kg bitumen per m3

0.18 m3
0.09 m3
0.27 m3
9.5 kg
5.1 kg

Total 14.6 kg

SEAL COAT
A. Liquid Seal Coat:
comprising of a layer of binder followed by a cover of
stone chipping
Stone chips shall be of 6.7mm size defined as 100 per
cent passing through 11.2 mm sieve and retained on
2.36 mm sieve. The quantity used for spreading shall
be 0.09 cubic metre per 10 square metre area.
B.Premixed Seal Coat:
a thin application of fine aggregates premixed with
bituminous binder
The quantity of bitumen shall be 9.8 kg and 6.8 kg per
10 m2 area for type A and type B seal coat respectively

CLOSELY GRADED PREMIX
CARPET/MIXED SEAL SURFACING
Close-graded premix carpet is a fairly
open graded mix
It is an alternative to the open graded
premix carpet and a seal coat
It may be constructed in one operation

AGGREGATE GRADATION FOR MSS
IS Sieve Cumulative % by wt. of total
aggregate passing
mm
Type A
Type B
13.2
100
11.2
100
88-100
5.6
52-88
31-52
2.8
14-38
5-25
0.09
0-5
0-5

POOR CONSTRUCTION OF MSS

Tack Coat on
Cracked
Bituminous
Surface

Thin Layer of MSS
over WBM

QUANTITY OF AGGREGATES AND
BITUMEN
The total quantity of aggregates
used shall be 0.27 cum per 10 m2 area
The quantity of binder shall be
22.0 kg and 19.0 kg for 10m2 area for
Type A and Type B surfacing
respectively

BITUMINOUS SURFACE COURSES

BITUMINOUS CONCRETE (BC)
BC is a Dense Graded Bituminous
Mix used as Wearing Course for
Heavily Trafficked Roads

BITUMINOUS CONCRETE (BC)
BC Mix consists of Coarse
Aggregates, Fine Aggregates, Filler
and Binder blended as per Marshall
Mix...
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